; OVRSWITCH ;--------------------------------------------------------------- ;! specifies when IMAGR switches from OVERLAP >= 2 to OVERLAP = 1 mode ;# ADVERB IMAGING ;----------------------------------------------------------------------- ;; Copyright (C) 2009 ;; Associated Universities, Inc. Washington DC, USA. ;; ;; This program is free software; you can redistribute it and/or ;; modify it under the terms of the GNU General Public License as ;; published by the Free Software Foundation; either version 2 of ;; the License, or (at your option) any later version. ;; ;; This program is distributed in the hope that it will be useful, ;; but WITHOUT ANY WARRANTY; without even the implied warranty of ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ;; GNU General Public License for more details. ;; ;; You should have received a copy of the GNU General Public ;; License along with this program; if not, write to the Free ;; Software Foundation, Inc., 675 Massachusetts Ave, Cambridge, ;; MA 02139, USA. ;; ;; Correspondence concerning AIPS should be addressed as follows: ;; Internet email: aipsmail@nrao.edu. ;; Postal address: AIPS Project Office ;; National Radio Astronomy Observatory ;; 520 Edgemont Road ;; Charlottesville, VA 22903-2475 USA ;----------------------------------------------------------------------- OVRSWTCH LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC ---------------------------------------------------------------- OVRSWTCH Type: Adverb (scalar) Use: To specify when OVERLAP >= 2 mode is changed to OVERLAP = 1 mode while Cleaning single-Gaussian, multi-facet images in IMAGR. The mode is switched when the peak residual reaches abs(OVRSWTCH) Jy/beam. If OVRSWTCH < 0, ONEBEAM is changed to TRUE for the OVERLAP = 1 portion of the Clean. Null value: 0.0 Do not switch modes Tasks: IMAGR......Fourier transforms and Cleans uv data with wide-field, interactive TV, and data weighting options. In OVERLAP=2 mode, AIPS images all facets to begin with and then Cleans only one. It subtracts the components from the residual uv data, chooses another facet, images it with the new residual data, Cleans it, and so forth. This has the desirable attribute of avoiding the sidelobes of the strong sources as they might appear in other facets because they are subtracted before those facets are imaged and Cleaned. OVERLAP=1 mode images all facets at once, Cleans them all, then subtracts any components found in all factes from the residual uv data, and then re-images and Cleans all facets again. It may be appropriate to start in OVERLAP=2 mode until the highest dynamic range structures are removed and then, when the Cleaning gets down near the noise levels, switch to OVERLAP=1 mode for the last portion of the Clean. OVRSWTCH is used to define the residual brightness level at which this switch will occur. ----------------------------------------------------------------